4.3 Write y=mx+b from given values
slope-intercept form: y=mx+b
[Handy if you know m & (0,b)]
Name: _______________________
Per _____
*point-slope form: y–y1 = m(x-x1)
[Handy if you know m & (x,y)]
* Most-useful for ANY situation. This is a no-fail formula for finding the equation of a line.
Use m & b to write the equation of a line in slope-intercept form.
1. y = _________________
2. y = _________________
3. y = _________________
m = 2/3 b = (0,9)
4. y = _________________
m = 7/3 b = (0,0)
7. y = _________________
slope is -4 y-intercept is 17
5. y = _________________
slope is – ½ y-intercept is 15
8. y = _________________
m= -1 b = (0,-11)
6. y = _________________
m= 0 b = (0,-11)
9. y = _________________
Parallel to y=1/2x, b = (0,3)
Parallel to y=3x+4
y-intercept is -1
Parallel to y=x+4, b = (0,- ½ )
10. y = _________________
11. y = _________________
12. y = _________________
13. y = _________________
14. y = _________________
15. y = _________________
X
Y
X
Y
X
Y
4
9
0
3
4
6
0
8
7
5
2
5
The purpose of the next few problems are just for you to practice using point-slope form.
Use the given slope and point to write the equation in point-slope form. Be careful with
the negatives. Your answer should look like: y – y1 = m(x – x1)
16. m = 3 point = (3,8)
19. m =
−3
2
point = (7,2)
22. m = -1 point = (0,3)
17. m = -2 point = (7,4)
20. m =
−13
15
point = (-2,8)
23. m = 0 point = (6,0)
18. m =
1
5
point = (11,1)
21. m = 1 point = (-5,-8)
24.
m = -7 point = (0,0)
Write the equation in point-slope form first, THEN change it into slope-intercept form.
Go from point-slope form: y – y1 = m(x – x1) to slope-intercept form: y=mx+b
25. m = 1 point = (4,2)
26. m = 2 point = (1,3)
27. m = -3 point = (3,4)
28. m = 4 point = (5,-1)
31. m =
1
2
point = (6,5)
29. m = -3 point = (2,-3)
32. m =
4
5
point = (15, 7)
30. m = -6 point = (-2,-3)
33. m =
−6
7
point = (-7,-1)
Find slope (m). THEN use m and one of the points to write the equation in point-slope
form: y – y1 = m(x – x1). FINALLY, write the equation in slope-intercept form: y=mx+b.
Yep, three steps to do here. 
34. (4, 8) & (2, 4)
35. (4, 12) & (1, 6)
36. (7, 9) & (4, 12)
37. (6, 6) & (4, 5)
38. (8, 9) & (6, 10)
39. (15, 12) & (10, 9)
40. (-1, 4) & (-4, 1)
41. (0, 2) & (-1, -5)
42. (-5, -2) (-4, -2)
43. EXTRA CREDIT
(-3, -4) (-10, -5)